Thanks for the response, Stray. I hate that your sister had to go through the same thing, it's so painful. I agree completely that an animal shouldn't suffer, and my cat has not shown any outward signs of pain or ill feelings. He eats, plays, uses the litter box, cuddles, etc, as he normally would. He is doing amazingly well for a cat his age and in his condition, but I know his days are numbered. The vet is actually very impressed that he has gained weight and has not recommended euthanasia at this point. According to his labs, he is in what is considered final stage kidney disease though and I am prepared to make that call when it's time. Since my cat can't talk, I just wanted to know if kidney disease (not talking the complete shut down of kidneys) brings more subtle, day-to-day feelings of discomfort like headaches, pain, lethargy, that my cat might not be displaying.